1. Filed of the invention
The present invention pertains to shaped crystalline anionic clay-containing bodies and a process for the preparation thereof.
2. Description of the Prior Art
Examples of crystalline anionic clays include hydrotalcite, meixnerite, sjxc3x6grenite, pyroaurite, stichtite, reevesite, eardleyite, manassite, and barbertonite. Crystalline anionic clays have several applications in the catalyst field and as absorbents. For most commercial applications crystalline anionic clays are formed into shaped bodies such as spheres. In all applications where shaped bodies are exposed to severe processing conditions and environments, such as oil refinery applications, separations, purifications, and absorption processes, it is of paramount importance that the integrity of the crystalline anionic clay-containing shaped bodies is kept intact and attrition is prevented.
In the prior art, crystalline anionic clays are usually incorporated into binder or matrix material in order to obtain attrition resistant shaped bodies. Commonly used binder or matrix material is alumina prepared from alumina precursors such as aluminum chlorohydrol, soluble aluminum salts, and acid dispersed pseudoboehmite; silica such as silica sols, silicates, silica-alumina cogels, and combinations thereof. Thus in EP-0 278 535 FCC additive or catalyst particles are described which are prepared by embedding hydrotalcite and optionally zeolite in a silica, silica-alumina or alumina matrix. To this end, hydrotalcite is slurried in a matrix precursor dispersion or solution and spray-dried.
However, when crystalline anionic clay is embedded in a matrix, the amount of active crystalline anionic clay ending up in the resulting shaped bodies is relatively small. There are applications in which for performance reasons it is desired that the shaped bodies consist or mostly consist of active crystalline anionic clay. Also, by the incorporation of crystalline anionic clay into matrix material, physical properties of the crystalline anionic clay such as specific surface area, pore size distribution; etcetera may be detrimentally affected. Further, the distribution of the crystalline anionic clay within the matrix is difficult to control. Another disadvantage of having to use a matrix to obtain attrition resistant bodies is the fact that most commonly used matrix/binder materials have some chemical activity, which in certain applications can cause undesirable side reactions. For instance, one of the most commonly used binder materials in FCC catalysts and additives is silica or silica based material. These types of binders are not suitable for use in sulfur oxides removal additives, because they detrimentally affect the sulfur removal.
In one embodiment, the present invention is directed to a process for the preparation of crystalline anionic clay-containing bodies from sources comprising an aluminum source and a magnesium source, comprising the steps of:
a) preparing a precursor mixture,
b) shaping the precursor mixture to obtain shaped bodies,
c) optionally thermally treating the shaped bodies, and
d) aging to obtain crystalline anionic clay-containing bodies.
In a second embodiment, the present invention comprises a crystalline anionic-clay-containing body wherein any binding material present in the body is present in a discontinuous phase.
Other embodiments of our invention encompass details about compositions, manufacturing steps, etc. all of which are hereinafter disclosed in the following discussion of each facets of the present invention.